High-voltage, field-effect transistors (HVFETs) are well known in the semiconductor arts. Many HVFETs employ a device structure that includes an extended drain region that supports or blocks the applied high-voltage (e.g., several hundred volts) when the device is in the “off” state. In a conventional vertical HVFET structure, a mesa of semiconductor material forms the extended drain or drift region for current flow in the on-state. A trench gate structure is formed near the top of the substrate, adjacent the sidewall regions of the mesa where the body region is disposed. Application of an appropriate voltage potential to the gate causes a conductive channel to be formed along the vertical sidewall portion of the body region such that current may flow vertically through the semiconductor material, i.e., from a top surface of the substrate where the source region is disposed, down to the bottom of the substrate where the drain region is located.